The invention relates to a method of manufacturing a semiconductor device, in which a base layer of photo-sensitive lacquer is applied to a surface of a semiconductor substrate, this layer being coated with a top layer of photosensitive lacquer, in which, by means of a patterned irradiation a mask is formed, which mask is used during a second irradiation as masking for a patterned irradiation of the base layer.
Such a method is more particularly suitable for the manufacture of semiconductor devices having a semiconductor substrate whose surface is not planar. In the manner described above, very narrow lacquer profiles having very steep edges can be formed in the base layer of a two-layer lacquer system comprising a base layer and a top layer. With the use of such a lacquer mask, it is possible, for example, to etch a a layer of a conductive material present on a non-planar surface to form conductive tracks whose width and separation are smaller than 1 .mu.m.
U.S. Pat. No. 4,362,809 discloses a method of the kind mentioned in the opening paragraph, in which a known photolacquer sensitive to radiation having wavelengths of 300 to 500 nm is used for the top layer and a layer of polymethylmethacrylate (PMMA) sensitive to radiation having wavelengths of 200 to 300 nm is used at the bad layer. After the first patterned irradiation in a so-called projection printer--in which a photolacquer mask is projected onto the top layer--, the top layer is developed in a usual developer. The mask thus formed in the top layer then consists of lacquer tracks located on the base layer, between which open spaces are present. The second irradiation is carried out by means of substantially parallel directed ultraviolet radiation having wavelengths of 200 to 300 nm, which is absorbed by the material of the top layer. Thus, a contact copy is formed in the base layer from the mask formed in the top layer.
By means of the known method described, lacquer tracks, whose width and separation are smaller than 1 .mu.m, can be formed in the base layer. However, this method has the disadvantage that a developing treatment in a wet developer is required for the conversion of the picture formed in the top layer by the first irradiation into a mask. This leads to additional processing steps because during the second irradiation the semiconductor substrate should be dry and clean again.